Early onset scoliosis and scoliosis in the growing spine poses a great challenge in their treatment. In progressive cases, the spine cannot usually be controlled by bracing or even casting and it will grow accentuating the deformity with all its known consequences. On the other hand, correction, fixation, and fusion of the spine will prevent further growth of the fused spine with serious effects on the development of the cardiovascular and pulmonary system, physical appearance, and psychological impacts.
Early onset scoliosis has more recently been treated surgically either by serial distractions or growth directed mechanisms. Serial distractions using “growing rod” systems have been more reliable and have achieved a more predictable outcome. These “growing rod” systems use tandem or domino connectors designed to allow periodic distractions (e.g., every few months) via surgical approach under anesthesia. Growth directed mechanisms have been used in “Luque Trolley” techniques applying segmental wires attached to the vertebrae and rods longer than the instrumented segment to allow for directed growth of the spine by forcing the spine to follow the rods. Some recent trials have used pedicle screws instead of wires—again allowing the heads of the screws attached to the vertebrae to slide along the longer rods with growth.
Both the “growing rod” and the “growth directed” mechanisms, in current systems, are far from being fully satisfactory in the treatment of early onset scoliosis. For example, the “growing rods” have to be distracted surgically every few months for many years with all the disadvantages of multiple surgeries and anesthetic administration in the pediatric age group. In addition to the problems arising from skin and soft tissue opening, the frequent force applied to distract these systems can cause implant failures in addition to the potential negative effects of forceful spinal cord distractions.
The “growth directed” and Luque Trolley type of segmental instrumentations do not require frequent distractions. These systems, however, have not been satisfactory, mainly due to their inability to control rotation, the loss of correction, and spontaneous fusion, which have led to their failure. Even after trials to replace the wires with pedicle screws, there are still many potential problems, including auto fusion after segmental exposure to insert the pedicle screws and a high possibility of jamming between the screw rod junctions preventing smooth gliding of the screws on the rod. Another problem includes the increased risk, time consumption, and radiation exposure needed to insert the large number of multilevel pedicle screws in this very young age group. Furthermore, in these systems, the amount of growth possible before another surgery is limited to the parts of the rod left protruding from the top and bottom screws.